Carrier separation analysis for clarifying leakage mechanism in unstressed and stressed HfAlOx/SiO2 stack dielectric layers

The carrier type involved in the leakage current through HfAlO_X/SiO₂ dielectric layers has been investigated for unstressed and stressed MOSFETs, using the carrier separation method. It is found that the hole current dominates the leakage current in the unstressed HfAlO_X/SiO₂. The dominant carrier in stress-induced leakage current (SILC) is hole, while the electron current is predominant after the soft breakdown (SBD) of the dielectric film. For the SILC condition, the trap generation in the high-k stack occurs both near the conduction band edge of n⁺poly-Si and the valence band edge of Si substrate. The defect sites generated in the high-k stack after SBD are located at energies near the conduction band edge of n⁺poly-Si.